The present invention relates to a non-biodegradable corneal implant and a method of preparing such an implant. More particularly, this invention relates to a non-biodegradable corneal implant comprising (1) a polymerized soluble transparent collagenous core having acylated amine groups or esterified carboxyl groups, and (2) a polymerized opaque periphery surrounding said core, said periphery comprising polymerized fibrous collagen, said collagen being in the form of fibrils under suitable physiological conditions. The corneal implant is useful in human corneal transplantation, for example, replacement of damaged cornea, corneal inlays or corneal onlays.
Much of the contents of U.S. Pat. No. 4,969,912 has been published. See, e.g., European Patent Application Publication No. 330,389, published Aug. 30, 1989.
Various materials have been described for use as transplantable corneal implants.
In U.S. Pat. Nos. 4,505,855 and 4,581,030 Bruns et al. disclose native, non-fibrilized transparent collagen material that can be fixed, i.e., cross-linked to form a prosthetic cornea replacement. The collagen material employed by Bruns et al. is soluble or rendered soluble by treatment with dilute acids, e.g., acetic acid; base, e.g., NaOH; and in dilute aqueous salts, e.g., NaCl. Bruns et al.'s pelleted collagen material is described as exhibiting strand like structures upon electron microscopic examination (see U.S. Pat. No. 4,505,855 and U.S. Pat. No. 4,581,030, col. 6, Example 3). However, the materials and corneal prosthesis disclosed in the Bruns et al. patents are not suitable for promoting cell ingrowth and enhancing the adhesion of the prosthesis to surrounding recipient tissue after transplantation.
In U.S. Pat. No. 4,772,283, White discloses a corneal implant prosthesis having a transparent lenticula to which is attached a carrier that is constructed from preserved biological tissue, e.g., cornea, sclera, fascia. The transparent lenticula can be made from a number of "non-biological materials", such as polymethylmethacrylate (PMMA), polycarbonates, polyhydroxyethylmethacrylate (HEMA), polysulfones and silicones. White's implant prosthesis is difficult to construct, however, because in order to attach such "non-biological" materials to the carrier, it is necessary to carry out elaborate and time consuming mechanical procedures, such as driving states into place where the lenticula and carrier are to be joined and heat fusing the tissue. Alternatively, the carrier tissue may be retained in the peripheral groove of the lenticula by crimping flanges which have been provided on the latter.
In U.S. Ser. No. 157,638 and European Patent Application Publication No. 330,389, there is disclosed a chemically modified, crosslinkable, solubilized collagenous substance obtained from autogenic intact human tissue, i.e., the donor and recipient are the same individual. This collagenous substance is useful as a corneal implant among others.
It would be highly desirable, therefore, to discover a corneal implant which would overcome the disadvantages of prior art materials, prosthesis, implants, and the like, such as the aforementioned construction problem and the difficulty in incorporating the implant into neighboring endogenous tissue of the recipient following transplantation.